Switch back to the GTX 660 bot on the CQ

It seems to be stable after upgrading to Debian 9.

Bug: skia:
Change-Id: I6c89f14748da177c9b0ede8da1da492564e66118
Reviewed-on: https://skia-review.googlesource.com/21361
Reviewed-by: Eric Boren <borenet@google.com>
Commit-Queue: Eric Boren <borenet@google.com>
1 file changed